The present invention generally relates to electric motors and more particularly to brush-holder systems for electric motors.
Electric motors that are used in power hand tools as well as other applications typically use brushes to provide electric interconnection with a motor commutator. As is well known in the motor art, the brushes that are used in electric motors are expendable items and must be periodically replaced over the lifetime of a motor that uses them. Motors that are used to power hand tools such as electric drills, saws and the like necessarily have a system for holding brushes that are used in the motors. Because motor brushes have a useful life that is much shorter than that of the tools in which they are used, it is often necessary to periodically replace the brushes that are worn out, which is usually much less costly to a user than replacing the entire tool.
While there have been many different designs of motors and their brush-holder systems, it was common for past systems to have brushes that were carried by brush-holders assembled in a motor housing that were secured with rubber pads, screws, end caps and the like. While some designs were more user friendly than others in that the brushes could be more easily replaced, many prior art configurations were not as convenient and adaptable to the periodic maintenance of replacing the motor brushes that were necessary to the operation of the motors.
While prior art designs utilized brush-holders that were often mounted in the motor end cap, for example, this type of design offered some advantages over prior designs in terms of the ease of replacement of the brushes. However, it was found that power hand tools that had brushes mounted in the end caps often experienced uneven performance because such power hand tools are susceptible to being dropped or shocked in one way or another. This occasionally resulted in some dysfunction or reduced performance because the force of impact from whatever source was imparted to the brush-holder assembly or the brushes themselves. Designs which isolate the brushes from impact as a result of the tool being dropped or otherwise subjected to abuse is a desirable goal.